1. Field of the Invention
This invention relates to wire guides used in diagnostic and interventional medical procedures. More specifically, this invention relates to wire guides used for access to complex distal anatomy for diagnostic and interventional procedures.
2. Related Technology
Wire guides (also known as guide wires) have been used in percutaneous entry procedures for diagnostic X-Ray studies and interventional procedures since about the 1950's when the idea of percutaneous, wire guided entry into the vasculature was conceived. As shown in FIGS. 18a and 18b, a wire guide U known in the prior art is typically inserted percutaneously into a body vessel V and advanced or manipulated within the body vessel V until reaching a desired location W. A catheter X (or other insertable device) is then positioned over the wire guide U, inserted percutaneously into the body vessel V, and advanced along the wire guide U to a desired location to perform a desired treatment, diagnosis, investigation, or medical intervention.
Therefore, wire guides typically have particular characteristics to improve the pushability of the wire guide U within the body vessel V. For example, the wire guide U is preferably generally radially flexible to negotiate the potentially-winding path of the body vessel V and to reduce potential damage to the body vessel walls while the wire guide U is being advanced. More specifically, wire guides U typically include a distal tip Y that is generally radially flexible. As another example, the wire guide shaft Z preferably has a relatively high axial stiffness to improve the pushability and control of the wire guide U along the body vessel V. The relatively high axial stiffness reduces kinking and bending so that the wire guide U will not become stuck or obstructed during the advancement thereof along the body vessel V. The axial stiffness of the wire guide shaft Z is preferably sufficient to prevent the wire guide U from folding over itself and becoming obstructed within the body vessel V when the distal tip Y encounters a bend in the body vessel V.
However, after being positioned as desired in the body vessel V, currently known wire guides may become tangled or obstructed during the advancement of the catheter X over the wire guide U. For example, the advancing catheter X may encounter a slightly curved portion of the wire guide U and undesirably exaggerate the curve of the wire guide U. More specifically, the curved wire portion may bend around the rim of the catheter X and bend the wire guide U into S-shaped curve Z, thereby resisting or preventing advancement of the catheter X.
It may be undesirable or difficult to improve the advanceability of the catheter along the wire guide by increasing the diameter or the axial stiffness of the wire guide because such a design change may decrease the pushability of the wire guide within the body vessel. For example, a wire guide with increased axial stiffness may not have enough radial flexibility to negotiate the winding path of the body vessel or may damage the body vessel while doing so. As another example, an increased-diameter wire guide may not be small enough to be received by the catheter or may be undesirably invasive to the body vessel.
Another disadvantage to the current design is that it may be difficult for the physician to keep the distal end of the wire guide properly positioned at the target site. For example, once the physician positions the wire guide at the desired location, the wire guide may migrate to another position within the body vessel. More specifically, the advancing catheter may bend the wire guide and cause the distal end of the wire guide to move from its desired position, as discussed above.
It is therefore desirous to provide a wire guide with a relatively small diameter that is able to be effectively pushed into a desired position, that is able to be received by a catheter, that is able to permit advancement of a catheter there along, and that is able to maintain its position at a desired location.